Nuclear Symmetry Energy Extracted From The (p,n) Charge Exchange Reaction Experimental Data

Nuclear symmetry energy attracts much attention in the field of nuclear physics. The nuclear symmetry energy Esym(ρ) is the energy related to neutron-proton asym-metry in the equation of state of nuclear matter. The nuclear symmetry energy Esym (ρ) plays an important role in both nuclear physics and astrophysics. Not only its magni-tude but also its density dependence is important to understand the structure of neutron-rich nuclei, the reaction mechanism of heavy-ion collisions, the structure of neutron stars and the dynamics of the supernova collapse. In the recent decades, there is much research effort aiming at extracting information about the nuclear symmetry energy, such as through analysing the nuclear mass with liquid drop models, various phenome-na in heavy-ion reactions and giant dipole resonances. There is already some constrain to the nuclear symmetry energy. But there is some difference between the different results given according to different extraction methods. More effort is still needed to investigate into the nuclear symmetry energy.In Chapter 1, we introduce the development of the nuclear symmetry energy. We also introduce two methods to extract the nuclear symmetry energy. One way is to analyse the nuclear mass in the droplet model, which helps us to extract the symmetry energy at saturation density. The other way is to analyse the heavy-ion collisions to extract the nuclear symmetry energy, which helps to restrain the nuclear symmetry energy in a larger range of density.In Chapter 2, we introduce the theoretical backgrounds of our work. Based on the Hugenhultz-Van Hove theorem, it has been shown analytically that both Esym(ρ0) and L(ρo) are determined by the nucleon optical potential. Thus by investigating the nucleon optical potential we can get some constraint for the nuclear symmetry energy. This provides us a new way to extract the nuclear symmetry energy. In this paper it is shown how we get the relation between the nuclear symmetry energy and the optical potential by using the HVH theorem. Besides, the optical potential has been used to fit nuclear reactions very well. The optical model to analyse the (p,n) charge exchange reaction is briefly introduced. By comparing the results with the experimental data we can get the value of the symmetry potential of the nucleon optical potential.In Chapter 3, the differential cross section of the (p,n) charge exchange reaction is analysed using the optical model. Through comparing the 13 data of 3 experiments with the theoretical results, the symmetry potential is obtained. Based on the error margin method, the error bar of the symmetry potential is obtained. And with the re-sults shown in Chapter 2, the values of the nuclear symmetry energy Esym(ρ0) and its density slope L are obtained. Together with the error bars of different terms contribut-ing to the value of the nuclear symmetry energy and its density slope, the calculated results Esym(ρ0)=28.5±2.0 MeV, L=67.0±5.0 MeV are obtained. It is shown that the results agree reasonably with those extracted by analysing nuclear masses and other experimental data.In Chapter 4, another way to extract the value of symmetry potential is given. The energies of the single particle states of the neutrons can be obtained by analysing the (d,p) stripping reaction data. It is observed that when 2 neutrons are added to a nucleus like 59Ni, its single particle neutron levels are displaced upwards in energy. The value of the symmetry potential can be extracted by analysing the change of the single particle states, from which we can get the value of the nuclear symmetry energy and its density slope.In Chapter 5, a summary of our work is given. We also make some outlooks of our work.